1. Field of the Invention
The present invention relates to a method, system, program, and data structure for cleaning a database table and, in particular, for performing clean operations on columns in the database table.
2. Description of the Related Art
Data records in a computer database are maintained in tables, which are a collection of rows all having the same columns. Each column maintains information on a particular type of data for the data records which comprise the rows. A data warehouse is a large scale database including millions or billions of records defining business or other types of transactions or activities. Data warehouses contain a wide variety of data that present a coherent picture of business or organizational conditions over time. Various data analysis and mining tools are provided with the data warehouse to allow users to effectively analyze, manage and access large-scale databases to support management decision making. Data mining is the process of extracting valid and previously unknown information from large databases and using it to make crucial business decisions. In many real-world domains such as marketing analysis, financial analysis, fraud detection, etc, information extraction requires the cooperative use of several data mining operations and techniques.
Once the desired database tables have been selected and the data to be mined has been identified, transformations on the data may be necessary. Transformations vary from conversions of one type of data to another, e.g., converting nominal values into numeric ones so that they can be processed by a neural network, to definition of new attributes, i.e., derived attributes. New attributes are defined either by applying mathematical or logical operators on the values of one or more database attributes. The transformed data is stored in a target database where it may then be mined using one or more techniques to extract the desired type of information necessary to make the organizational decisions. Further details of data mining are described in the International Business Machines Corporation (IBM) publication entitled “White Paper: Data Mining Solutions” (IBM Copyright, 1996)
Data transformation refers to the process of filtering, merging, decoding, and translating source data to create validated data for the data warehouse and data mining tools. For example, a numeric regional code might be replaced with the name of the region. Data transformations and cleansing is used when data is inconsistent or incompatible between sources. In such case, some level of data cleansing is needed to ensure data consistency and accuracy. Some of the current techniques for transforming and cleansing data include the use of an SQL WHERE clause to limit the rows extracted from the source table. Further, formulas and expressions specified in the column definition window and constants and tokens are used to eliminate and modify data.
Previous versions of IBM Visual Warehouse included programs to allow users to perform numerous functions on the source data. For instance, if one database table has revenue data in U.S. dollars and another data table stores revenue data in foreign currency denominations, then the foreign revenue data must be cleansed before both sets of data can be analyzed together. Transformation operations may be performed using application programs external to the database program that process and transform tables of data records. Further details of data warehousing and data transforms, are described in the IBM publications “Managing Visual Warehouse, Version 3.1,” IBM document no. GC26-8822-01 (IBM Copyright, January, 1998), which is incorporated herein by reference in its entirety.
Notwithstanding current programs for cleansing data, there is a need in the art to provide users greater control over operations to clean input data.